1. Field of the Invention
This invention relates to taking accurate dental impressions, from which indirect dental castings are fabricated.
2. Description of the Prior Art
Heretofore, impression trays have solid or perforated walls designed to cup over teeth. Dental impression trays are used to carry impression material to areas of the mouth and are used to support the moldable material until it cures. The tray is then utilized to remove the set material from the mouth.
A hardening material, such as dental stone or epoxy, is subsequently poured into the impression. Thus, a model is obtained when the die material has hardened and then recovered from the impression material. From this model, a prosthesis is fabricated to fit this area of the mouth.
Removing impression trays can be difficult because of suction existing between impression material and tissue surfaces while lifting away from oral structures. A very strong suction may distort the impression. Elasticity limits of impression material are often exceeded leaving an unknowingly distorted impression.
Present trays do not provide for venting of the impression when the tray is lifted. Resultant vacuum trap over teeth causes undue pressure on soft, fresh cured material.
Also, the tray may shift during setting by an inadvertent hand movement of the dentist or by the patient swallowing and moving the tongue. A tray, jarred during setting, will yield urnreliable results. Dentists today must support the tray by hand while impression material sets in the patient's mouth. Present trays do not provide for stabilization against tooth structures.
In U.S. Pat. No. 5,320,529, Pompa discloses a device for an implant drill guide. Guides utilized are in a splint, not in an impression tray. The operation is different from the present invention. Pompa's invention relates to drilling in a controlled area.
In U.S. Pat. No. 4,382,785, Lococo discloses a tray to receive impression material through orifices along the top, but does not provide for venting.
3. Objects of the Invention
An object of this invention is to produce a dental impression tray which will fit securely in one location. The tray rests on selected teeth and resists movement while impression material is setting.
Another object of the present invention is to allow certain selected areas of the impression tray to be vented. An open airway from occlusal surfaces of teeth to ambient air is established before the tray is removed.
Another object of the present invention is to provide an impression tray which increases accuracy and which provides a predictable fit, leaving the dentist with a more controllable means of fabricating a quality casting.
Another object of the present invention is to provide an impression tray which will aid dentists and laboratory technicians in the process of fabricating restorations.